MR Perfusion Methods in Patients With Suspected Recurrent High Grade Gliomas

Radiation therapy is an important adjunct in the treatment of patients with glioma, although a common side effect is radiation-induced injury of brain parenchyma. Unfortunately, conventional MRI is not accurate in differentiating radiation-induced brain injury from recurrent tumour, both of which may demonstrate progressive contrast enhancement. Recent studies have suggested that perfusion MRI could improve this differentiation. Perfusion MRI can be performed with an injection of exogenous contrast using dynamic contrast enhancement (DCE) or dynamic susceptibility contrast enhancement (DSC). Perfusion MRI can also be performed without contrast injection using arterial spin labeling (ASL) or intravoxel incoherent motion (IVIM). DCE-MRI relies on accurate measurement of T1 values in order to convert the MRI signal intensity to contrast concentration. Dynamic susceptibility-weighted contrast enhancement (DSC) perfusion is the most common technique used in clinical practice but measurement of tumor relative cerebral blood volume (rCBV) can be biased by extravascular contrast leakage and susceptibility-weighted artifacts. The purpose of this study is to evaluate the accuracy of perfusion MR imaging using non-contrast and contrast-based techniques in differentiating recurrent tumour from radiation-induced brain injury in patients with known high grade glioma. The investigators will compare the accuracy of IVIM, ASL, DCE and DSC techniques. A secondary goal of the study is to compare two new different T1 mapping methods used for DCE-MRI.